In this study we evaluated the role of angiotensin H (Ang H) receptors in the
spontaneous contractility of isolated myometrial strips from pregnant rat uterus.
A total number of 24 pregnant albino rats (in the last part of gestation) were
used. The animals were divided into four groups and we determined the changes in
the tone, frequency, and amplitude of contractions of isolated myometrial strips in
each group after administration of (1) Ang ri in a dose of 5, 10,20 rig/m1 (group 1),
(2) Ang I1+ATI receptor antagonist (Losartan) in a dose of 5 ng Ang 11+100 nmol
Losartan/yd. 10 ng Mg 11+100 nmol Losartan1/24 and 20 ng Ang 11+100 nmol
Losartan (group 2), (3) Losartan in a dose of 1, 10, 100 nmol/,.J (group 3) and (4)
angiotensin 11 converting enzyme inhibitor (Captopril in a dose of 5,10,20 pmol )
(group 4).
The results of this study demonstrated that Ang 11 induced a significant
concentration dependent increase in both tone and rhythmic oscillations of the uterine
smooth muscles. In addition, the small dose of Mg 11 increased the amplitude of
uterine contraction, while the other two large doses caused a concomitant decrease in
it. This effect was significantly reduced by ATI receptor antagonist (Losartan). In
addition, the ATI receptor antagonist (Losartan) when administered alone to the
uterine strips caused a significant concentration dependent decrease in the
contractility and rhythmic oscillations of the uterine smooth muscles. The study
revealed also that angiotensin converting enzyme inhibitor (Captopril ) caused a
significant dose dependent decrease in the frequency and amplitude of uterine
contraction. However, Captopril produced insignificant changes in the uterine tone.
We can conclude that angiotensin H receptors are present in the uterine tissues
and that angiotensin H seems to be formed locally by renin and angiotensin
converting enzyme in this tissues. This is in accordance with a functional renin
angiotensin system which may be important for contraction of the myometrial smooth
muscle cells.
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